package com.ky.leetcode.剑指Offer;

import java.util.Stack;

/*

用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 )

    示例 1：
    输入：
    ["CQueue","appendTail","deleteHead","deleteHead"]
    [[],[3],[],[]]
    输出：[null,null,3,-1]

    示例 2：
    输入：
    ["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
    [[],[],[5],[2],[],[]]
    输出：[null,-1,null,null,5,2]
    提示：

    1 <= values <= 10000
    最多会对 appendTail、deleteHead 进行 10000 次调用

 */
public class 剑指Offer09用两个栈实现队列 {

    public static void main(String[] args) {
        CQueue cQueue = new CQueue();
        System.out.println(cQueue.deleteHead());
        cQueue.appendTail(5);
        cQueue.appendTail(2);
        System.out.println(cQueue.deleteHead());
        System.out.println(cQueue.deleteHead());
    }

    public static class CQueue {

        private Stack<Integer> appendStack;
        private Stack<Integer> deleteStack;

        public CQueue() {
            appendStack = new Stack<>();
            deleteStack = new Stack<>();
        }

        public void appendTail(int value) {
            appendStack.push(value);
        }

        public int deleteHead() {
            if (deleteStack.isEmpty()) {
                if (appendStack.isEmpty()) {
                    return -1;
                } else if (appendStack.size() == 1) {
                    return appendStack.pop();
                } else {
                    while (!appendStack.isEmpty()) {
                        deleteStack.push(appendStack.pop());
                    }
                    return deleteStack.pop();
                }
            } else {
                return deleteStack.pop();
            }
        }
    }

/**
 * Your CQueue object will be instantiated and called as such:
 * CQueue obj = new CQueue();
 * obj.appendTail(value);
 * int param_2 = obj.deleteHead();
 */

}
